Nickel electroplating solution and chip parts using the same

ABSTRACT

Disclosed herein is a nickel electroplating solution and chip parts using the same, and more particularly, to a nickel electroplating solution including: nickel metal; nickel chloride; boric acid; a first additive of at least one selected from a group consisting of benzene, naphthalene, xylene, sulfonic acid, sodium sulfonate, and saccharine (C 7 H 5 NO 3 S); and a second additive of at least one selected from a group consisting of sodium dialkyl sulfosuccinate, sodium lauryl sulfate, polyethylene glycol, polyethylene glycol methylether, and polyethylene glycol lauryl amineether to have excellent smoothness and wettability, thereby forming a nickel electroplating layer which is uniform and smooth and has no unplated part and improve soldering characteristics regardless of the surface state and structural shape of an external terminal electrode which is a plated article, and chip parts using the same.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. Section [120, 119, 119(e)] of Korean Patent Application Serial No. 10-2010-0092502, entitled “Nickel Electroplating Solution And Chip Parts Using The Same” filed on Sep. 20, 2010, which is hereby incorporated by reference in its entirety into this application.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a nickel electroplating solution capable of forming a nickel electroplating layer that is uniform and smooth and has no unplated part and improving soldering characteristics regardless of the surface state and structural shape of an external terminal electrode which is a plated article, and chip parts using the same.

2. Description of the Related Art

In general, in a chip part, both external terminal electrodes 14 connected with an inner electrode 13 are formed at both ends of a dielectric element 11 in which an internal electrode 13 having a predetermined pattern is printed on a dielectric sheet 12 and a plating layer 15 for improving soldering characteristics with a printed circuit board (PCB) is formed in the external terminal electrode 14 as shown in FIG. 1.

The plating layer 15 is made of tin (Sn), nickel (Ni), tin/plumbum (Sn/Pb), nickel/tin (Ni/Sn), nickel/tin/plumbum (Ni/Sn/Pb), or the like by using an electroplating method for selectively plating only the external terminal electrode 14 having conductivity. Among them, the tin (Sn) plated layer is used to improve a bonding property with a solder and the nickel (Ni) plated layer serves as a barrier layer between the external terminal electrode 14 and the solder and is generally formed by using a nickel plating solution without an additive.

However, in the case where the surface state of a plated article such as the external terminal electrode 14 is not good and the surface roughness of the external terminal electrode 14 is large, a nonuniform plated film may be obtained or a partial unplating phenomenon may occur at the time of forming the plating layer 15. Further, even in the case where the plated article is structurally curved, contact between the plated article and the plating solution is not good, such that the partial unplating phenomenon may occur. For example, since the plated article having the external terminal electrode formed at the outer portion of a product by processing a through-hole is spatially narrower than a structure in which the inside of a hole is directly exposed to the plating solution, wettability of the plated article in the plating solution is not smoothly ensured. In this case, a smooth nickel plating layer is difficult to form and minute air bubbles are collected in the hole, such that the partial unplating phenomenon occurs.

As such, when the plating layer is formed by using the known nickel plating solution without the additive, it is difficult to resolve plating defect problems such as the nonuniform plating layer and the partial unplating phenomenon. Further, due to the plating defects, even after the tin plated layer which is a final plating layer of the chip part is formed, the unplated part is still externally observed and soldering characteristics of the plated layer of the chip part are deteriorated even in reliability evaluation.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a nickel electroplating solution capable of forming a nickel plated layer having no defect such as a nonuniform plated film or a partial unplating phenomenon regardless of the surface state and structural shape of an external terminal electrode which is a plated article.

Another object of the present invention is to provide chip parts using the nickel electroplating solution.

According to an exemplary embodiment of the present invention, there is provides a nickel electroplating solution including: nickel metal; nickel chloride; boric acid; a first additive of at least one selected from a group consisting of benzene, naphthalene, xylene, sulfonic acid, sodium sulfonate, and saccharine (C₇H₅NO₃S); and a second additive of at least one selected from a group consisting of sodium dialkyl sulfosuccinate, sodium lauryl sulfate, polyethylene glycol, polyethylene glycol methylether, and polyethylene glycol lauryl amineether.

The first additive may be included with 5 to 30 g/L.

The second additive may be included with 0.05 to 5 g/L.

Further, the present invention provides a chip part including a nickel plated layer formed by using the nickel electroplating solution as a barrier layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a general chip part;

FIG. 2 is a photograph of a scanning electron microscope (SEM) illustrating an appearance of a chip part after forming a tin plated layer on a nickel plated layer formed in a second example of the present invention;

FIG. 3 is a photograph of an optical microscope illustrating a cross section after forming the tin plated layer on the nickel plated layer formed in Example 2 of the present invention; and

FIG. 4 is a photograph of a scanning electron microscope (SEM) illustrating an appearance of a chip part after forming a tin plated layer on a nickel plated layer formed in a first comparative example of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to a nickel electroplating solution capable of forming a nickel electroplating layer without a plating defect and improving soldering characteristics and chip parts using the same.

Hereinafter, the present invention will be described in detail.

The nickel electroplating solution includes nickel metal, nickel chloride, boric acid, a first additive, and a second additive.

Nickel metal, nickel chloride, and boric acid are basic components of the nickel electroplating solution. Nickel metal of 60 to 100 g/L, nickel chloride of 20 to 60 g/L, and boric acid of 20 to 60 g/L may be contained in the nickel electroplating solution. When the basic components are contained with the contents, it is possible to achieve a nickel electroplating solution having high stability because nickel is easily dissolved and nickel is almost not precipitated.

In the present invention, the basic components include both the first additive providing smoothness and the second additive capable of improving wettability as additives.

The first additive as a compound capable of forming a nickel plated layer which is uniform and smooth regardless of the surface state and structural shape of a plated article by providing smoothness to the nickel plated layer is made of preferably at least one selected from a group consisting of benzene, naphthalene, xylene, sulfonic acid, sodium sulfonate, and saccharine (C₇H₅NO₃S) and more particularly, saccharine (C₇H₅NO₃S).

The first additive is contained in the nickel electroplating solution with preferably 5 to 30 g/L and more preferably 10 to 20 g/L. When the content of the first additive is less than 5 g/L, a smoothness providing effect of the nickel plated layer may be minimal and when the content is more than 30 g/L, the stability of the electroplating solution may be deteriorated and carbon codeposition are generated in the nickel plated layer to deteriorate soldering reliability.

The second additive is a compound capable of forming a nickel plated layer which is uniform and smooth and has no unplated part by smoothly contacting the electroplating solution and the plated article regardless of the surface state and structural shape of the plated article by improving wettability of the nickel electroplating solution, for example, by smoothly wetting the electroplating solution to a narrow portion of the plated article such as a curve or a through-hole.

The second additive preferably includes: anionic surfactants including sodium dialkyl sulfosuccinate such as sodium diisobutyl sulfosuccinate, sodium dihexyl sulfosuccinate, sodium dicyclohexyl sulfosuccinate, and sodium dioctyl sulfosuccinate, and sodium lauryl sulfate; and nonionic surfactants including polyethylene glycol, polyethylene glycol methylether, polyethylene glycol lauryl amineether, and the like, and more preferably, sodium dialkyl sulfosuccinate. They may be used singly or by mixing two or more.

The second additive is contained in the nickel electroplating solution with preferably 0.05 to 5 g/L and more preferably 0.1 to 3 g/L. When the content of the second additive is less than 0.05 g/L, a wettability improvement effect of the nickel electroplating solution is minimal and when the content is more than 5 g/L, workability is deteriorated to be inappropriate due to carbon codeposition and foaming in the nickel plated layer.

The nickel electroplating solution may be fabricated by mixing the components with each other and as necessary, agitating them and adjusting pH between 3 and 5 with sulfuric acid or nickel hydroxide.

The nickel plated layer may be formed by electroplating at 45 to 55° C. with the nickel electroplating solution.

The nickel plated layer may be a barrier layer between an external terminal electrode and a solder.

Further, the present invention provides a chip part including the nickel plated layer as the barrier layer.

A tin plated layer may further be formed on the nickel plated layer which is the barrier layer.

Hereinafter, exemplary embodiments will be described in order to help the understanding of the present invention. However, they do not limit the appended claims but just illustrate the exemplary embodiments. Therefore, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

EXAMPLES Example 1

A first additive, saccharine of 15 g/L and a second additive, sodium lauryl sulfate of 0.5 g/L were added and agitated to a basic component in which nickel metal of 80 g/L, nickel chloride of 40 g/L, and boric acid of 40 g/L were mixed. A nickel electroplating solution was prepared by adjusting pH between 3 and 5 by using sulfuric acid and nickel hydroxide.

A plated article having a curve on the surface thereof is electroplated with the prepared nickel electroplating solution at 50° C. to form a nickel plated layer.

Further, a tin electroplating solution is electroplated on the nickel plated layer to form a tin plated layer.

Example 2

A first additive, saccharine of 15 g/L and a second additive, sodium dihexyl sulfosuccinate of 1 g/L were added and agitated to a basic component in which nickel metal of 80 g/L, nickel chloride of 40 g/L, and boric acid of 40 g/L are mixed. A nickel electroplating solution was prepared by adjusting pH between 3 and 5 by using sulfuric acid and nickel hydroxide.

A nickel plated layer and a tin plated layer were formed using this plating solution in the same method as Example 1 described above.

Example 3

A first additive, saccharine of 4 g/L and a second additive, sodium dihexyl sulfosuccinate of 1 g/L were added and agitated to a basic component in which nickel metal of 80 g/L, nickel chloride of 40 g/L, and boric acid of 40 g/L were mixed. A nickel electroplating solution was prepared by adjusting pH between 3 and 5 by using sulfuric acid and nickel hydroxide.

A nickel plated layer and a tin plated layer were formed using this plating solution in the same method as Example 1 described above.

Example 4

A first additive, saccharine of 31 g/L and a second additive, sodium dihexyl sulfosuccinate of 1 g/L were added and agitated to a basic component in which nickel metal of 80 g/L, nickel chloride of 40 g/L, and boric acid of 40 g/L were mixed. A nickel electroplating solution was prepared by adjusting pH between 3 and 5 by using sulfuric acid and nickel hydroxide.

A nickel plated layer and a tin plated layer were formed using this plating solution in the same method as Example 1 described above.

Example 5

A first additive, sodium sulfonate of 15 g/L and a second additive, sodium dihexyl sulfosuccinate of 1 g/L were added and agitated to a basic component in which nickel metal of 80 g/L, nickel chloride of 40 g/L, and boric acid of 40 g/L were mixed. A nickel electroplating solution was prepared by adjusting pH between 3 and 5 by using sulfuric acid and nickel hydroxide.

A nickel plated layer and a tin plated layer were formed using this plating solution in the same method as Example 1 described above.

Comparative Example 1

Nickel metal of 80 g/L, nickel chloride of 40 g/L, and boric acid of 40 g/L were mixed with each other and pH is adjusted between 3 and 5 by using sulfuric acid and nickel hydroxide so as to prepare a nickel electroplating solution.

A nickel plated layer and a tin plated layer were formed using this plating solution in the same method as Example 1 described above.

Comparative Example 2

Only a first additive, saccharine of 15 g/L is was added and agitated to a basic component in which nickel metal of 80 g/L, nickel chloride of 40 g/L, and boric acid of 40 g/L were mixed. A nickel electroplating solution is prepared by adjusting pH between 3 and 5 by using sulfuric acid and nickel hydroxide.

A nickel plated layer and a tin plated layer were formed using this plating solution in the same method as Example 1 described above.

Comparative Example 3

Only a second additive, sodium lauryl sulfate of 0.5 g/L was added and agitated to a basic component in which nickel metal of 80 g/L, nickel chloride of 40 g/L, and boric acid of 40 g/L were mixed. A nickel electroplating solution was prepared by adjusting pH between 3 and 5 by using sulfuric acid and nickel hydroxide.

A nickel plated layer and a tin plated layer were formed using this plating solution in the same method as Example 1 described above.

The components and contents (g/L) of the nickel electroplating solutions prepared in the examples and comparative examples are shown in Table 1 below.

TABLE 1 second additive first additive sodium sodium Classifi- nickel nickel boric sodium lauryl dihexyl cation metal chloride acid accharine sulfonate sulfate sulfosuccinate Example 1 80 40 40 15 — 0.5 — Example 2 80 40 40 15 — — 1 Example 3 80 40 40  4 — — 1 Example 4 80 40 40 31 — — 1 Example 5 80 40 40 — 15 — 1 Comparative 80 40 40 — — — — Example 1 Comparative 80 40 40 15 — — — Example 2 Comparative 80 40 40 — — 0.5 — Example 3

The nickel plated layers and the tin plated layers formed on the nickel plated layers that were prepared in the examples and the comparative examples were verified using a scanning electron microscope (SEM) and an optical microscope.

In the case of the nickel plated layers formed by using nickel electroplating solutions of Examples 1 to 5, which include the first and second additives in addition to nickel metal, nickel chloride, and boric acid, even though a plated article having a curved surface is electroplated, the electroplating solution is smoothly wetted to the plated article to achieve a plated layer of which the surface is uniform and smooth and has no unplated part. Particularly, when the first additive is included with 5 to 30 g/L and the second additive, sodium dihexyl sulfosuccinate of 0.05 to 5 g/L was used, it was possible to obtain the best plated layer without deterioration of workability.

As shown in FIG. 2 (SEM), a partial unplating phenomenon does not occur at the time of preparing the nickel plated layer and the uniform and smooth nickel plated layer was formed by using the nickel electroplating solution of Example 2, as a result, it is possible to verify that the state of the tin plated layer formed on the nickel plated layer is excellent. Further, as shown in the cross-sectional view of FIG. 3 (optical microscope), the smooth nickel plated layer was formed while filling the curved part of the plated article and the tin plated layer was formed thereon.

In contrast, the nickel plated layers formed by using the nickel electroplating solutions of Comparative Examples 1 to 3 not including both the first and second additives or including only any one therebetween were difficult to satisfy smoothness and wettability, such that the unplated part was partially generated. As a result, a plating defect was observed at the time of forming the tin plated layer.

As shown in FIG. 4 (SEM), in the case of using the nickel electroplating solution of Comparative Example 1, the unplated part was generated in the nickel plated layer, as a result, a lower part of the plated article was partially exposed and in the case of forming the tin plated layer in the corresponding part, the plating defect occurred.

According to examples of the present invention, a nickel electroplating solution can form a nickel electroplating layer which is uniform and smooth and has no unplated part regardless of the surface state and structural shape of an external terminal electrode which is a plated article by containing a first additive capable of providing smoothness and a second additive improving wettability.

Further, it is possible to achieve high reliability by improving soldering characteristics in chip part plating by including a nickel plating layer as a barrier layer between the external terminal electrode and a solder.

Although the examples of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Accordingly, the spirit and scope of the present invention is not limited to the examples and should be defined by the appended claims and the equivalents thereoto. 

1. A nickel electroplating solution, including: nickel metal; nickel chloride; boric acid; a first additive of at least one selected from a group consisting of benzene, naphthalene, xylene, sulfonic acid, sodium sulfonate, and saccharine (C₇H₅NO₃S); and a second additive of at least one selected from a group consisting of sodium dialkyl sulfosuccinate, sodium lauryl sulfate, polyethylene glycol, polyethylene glycol methylether, and polyethylene glycol lauryl amineether.
 2. The nickel electroplating solution of claim 1, wherein sodium dialkyl sulfosuccinate is selected from a group consisting of sodium diisobutyl sulfosuccinate, sodium dihexyl sulfosuccinate, sodium dicyclohexyl sulfosuccinate, and sodium dioctyl sulfosuccinate.
 3. The nickel electroplating solution of claim 1, wherein the first additive is included with 5 to 30 g/L.
 4. The nickel electroplating solution of claim 3, wherein the first additive is included with 10 to 20 g/L.
 5. The nickel electroplating solution of claim 1, wherein the second additive is included with 0.5 to 5 g/L.
 6. A chip part including a nickel plated layer formed by using a nickel electroplating solution of claim 1 as a barrier layer. 